What type of gases holds in heat and keeps the earth at a moderate temperature?
a. primary gases
b. ozone layer
c. trace gases
d. greenhouse gases

All of the following were pre-columbian civilizations in latin america, except

What was the first official pair of sister cities?

Trade routes emerged along which coast when arab and indian traders from around the indian ocean mixed with the bantu people from africa's interior? a. swahili coast b. guinea coast c. drakensberg coast d. namib coast